1. Field of the Invention
The present invention relates generally to integrated circuit memory devices, and more specifically to a structure for utilizing a portion of an embedded memory.
2. Description of the Prior Art
During the manufacture of integrated circuit memory devices, die are often discarded because a portion of the die is defective and can not be repaired at, for instance, laser repair. Even though a major portion of the die may be fully functional, it is often necessary to discard the entire die as scrap because the functional portion of the die is not recoverable. For instance, it is not uncommon to scrap a 64K SRAM die which is partially functional and could yield a 16K SRAM. Even though the 64K SRAM could be used as a smaller 16K SRAM device, it must be scrapped if there is no plausible method to recover the functional portion.
This concern for recovering a portion of an integrated circuit die extends fully to embedded memories which find a wide variety of uses in devices such as application specific integrated circuits (ASICs) and microprocessors. In microprocessor devices, a significant amount of embedded memory is often required; for instance, the Intel i860 RISC processor and the MIP R4000 processor both have 32K bytes of on-chip and cache memory. Additionally, Texas Instrument's Super SPARC processor has 36K bytes of internal memory. In the future, it is likely that both processors and ASICs will continue to house larger and larger amounts of memory.
As the need for larger embedded memories grows, the yield constraints driven by manufacturing concerns will grow as well. Redundancy testing has typically been used to test for functionality, but this method may not be sufficient or practical for larger embedded memories. As a result, microprocessors or ASICs which may be fully functional, other than having a partially functional embedded memory, may be scrapped. Because of the high price and profit margin associated with these devices, it becomes important to recover embedded memory if possible so that scrapping is kept to a minimum.